The heating should be turned down in classrooms to stop teachers and children getting tired, the largest education union in the UK has said.
The National Education Union (NEU) believes that being too hot can lead to staff and children suffering from fatigue and ill health.
Currently there are regulations in place to ensure that classrooms are not too cold, however no maximum temperature exists.
Regulation 7 of the Workplace Regulations 1992 merely states that during working hours, the temperature inside all workplace buildings should be reasonable.
Now the union has said a maximum temperature is needed to protect the well-being of children and school staff.
The union recommends that a maximum temperature of 26 degrees celsius would be acceptable.
Kevin Courtney, joint general secretary of the NEU, said: “High temperatures in schools affect the ability of pupils, teachers and staff to concentrate and work effectively and can lead to tiredness, fatigue and ill health.
“Currently, there is no legal maximum temperature for schools and colleges and this can lead to uncomfortable conditions during hot weather. The National Education Union advises its members that temperatures above 26C are too hot for effective teaching and learning.
“The NEU strongly supports the introduction of a maximum legal temperature in schools in order to protect the health and well-being of children and school staff”.
High temperatures in schools affect the ability of pupils, teachers and staff
Kevin Courtney, joint general secretary of the NEU
The plea follows fresh calls from the Educational Institute of Scotland (EIS) to impose a similar guideline north of the border.
EIS general secretary Larry Flanagan said: "School classrooms are not just accommodation; they are learning environments each requiring their own specific temperatures.
"Schools sometimes send pupils home when the school is too cold - but we also need to be aware of the potential risk of classrooms being too hot for pupils and teachers to work in safely."
Mr Flanagan wants the Scottish government to give serious consideration to the issue of maximum temperature in order to ensure appropriate learning conditions for pupils.